Fluoride is a common active ingredient in tooth paste to prevent dental caries. It is also added or removed from the water supply in some communities for the same reason, but in children only.

My understanding is that the fluoride in tooth paste reacts with minerals in saliva then bonds to the tooth enamel. The fluoride in water is ingested and is somehow added to the developing bones and teeth of growing children, to the benefit of making decay resistant teeth.

What is the biochemical pathway of each process? A perfect answer will also discuss fluorosis and when that occurs and why.